SELECTIVE LASER MELTING OF INTERMETALLIC TITANIUM ALLOY

The in-situ synthesis of the Ti2AlNb-based intermetallic alloy using selective laser melting of powder materials was studied. The object of research is the Ti–22Al–25Nb alloy (at.%), the main phase of which is the Ti2AlNb intermetallic compound with an ordered orthorhombic lattice (O phase). The Ti–22Al–25Nb alloy has good mechanical properties at room and elevated temperatures, low specific weight, and is considered as a promising material for aerospace industry applications. Experiments used a mechanical mixture of pure titanium, aluminum and niobium powders in a ratio required for Ti–22Al–25Nb alloy synthesis. Selective laser melting as an additive technology is the most promising way for additive layer manufacturing of parts. This technology allows manufacturing complex-shaped items based on CAD model data. Selective laser melting was used to make compact samples for investigations. Their microstructure, density, phase composition and microhardness were studied. In addition, the effect of heat treatment homogenization at 1250 °C for 2,5 h and then aging at 900 °C for 24 h on the microstructure and chemical homogeneity of samples were studied. It was shown that the compact material obtained by selective laser melting contains unmelted niobium particles. Homogenization annealing makes it possible to dissolve these particles completely in the alloy. As a result, the material microstructure consists of B2 phase grains of different sizes and needle-like precipitates of the orthorhombic phase.

1. Lütjering G., Williams J.C. Titanium. Berlin: Springer Berlin Heidelberg, 2007.

2. Kim Y.-W. Ordered intermetallic alloys. Pt. III: Gamma titanium aluminides. JOM. 1994. Vol. 46. P. 30—39.

3. Gogia A.K., Nandy T.K., Banerjee D., Carisey T., Strudel J.L., Franchet J.M. Microstructure and mechanical properties of orthorhombic alloys in the Ti—Al—Nb system. Intermetallics. 1998. Vol. 6. P. 741—748.

4. Chen W., Li J.W., Xu L., Lu B. Development of Ti2AlNb alloys: opportunities and challenges. Adv. Mater. Process. 2014. Vol. 172. P. 23—27.

5. Appel F., Paul J.D.H., Oehring M. Gamma titanium aluminide alloys: Science and technology. John Wiley & Sons, 2011.

6. Popovich A., Sufiiarov V. Metal powder additive manufacturing: Chapter 10. In: New trends in 3D printing. London: InTech, 2016. Р. 215—236.

7. Smelov V.G., Sotov A.V., Agapovichev A.V., Tomilina T.M. Selective laser melting of metal powder of steel 3161. IOP Conf. Series: Mater. Sci. Eng. 2016. Vol. 142. No. 1. P. 012071.

8. Popovich A., Sufiiarov V., Polozov I., Borisov E., Masaylo D., Orlov A. Microstructure and mechanical properties of additive manufactured copper alloy. Mater. Lett. 2016. Vol. 179. P. 38—41.

9. Holzweissig M.J., Taube A., Brenne F., Schaper M., Niendorf T. Microstructural characterization and mechanical performance of hot work tool steel processed by selective laser melting. Metall. Mater. Trans. B. 2015. Vol. 46. No. 2. P. 545—549

10. Popovich A., Sufiiarov V., Borisov E., Polozov I. Microstructure and mechanical properties of Ti—6Al—4V manufactured by SLM. Key Eng. Mater. 2015. Vol. 651— 653. P. 677—682.

11. Wang G., Yang J., Jiao X. Microstructure and mechanical properties of Ti—22Al—25Nb alloy fabricated by elemental powder metallurgy. Mater. Sci. Eng. A. 2016. Vol. 654. P. 69—76.

12. Froes F.H., Mashl S.J., Hebeisen J.C., Moxson V.S., Duz V. The technologies of titanium powder metallurgy. JOM. 2004. Vol. 56. P.46—48.

13. Wang Y.H., Lin J.P., He Y.H., Wang Y.L., Lin Z., Chen G.L. Reaction mechanism in high Nb containing TiAl alloy by elemental powder metallurgy. Trans. Nonferr. Met. Soc. China (Engl. ed.). 2006. Vol. 16. P. 853—857.

14. Fischer M., Joguet D., Robin G., Peltier L., Laheurte P. In situ elaboration of a binary Ti— 26Nb alloy by selective laser melting of elemental titanium and niobium mixed powders. Mater. Sci. Eng. C. 2016. Vol. 62. P. 852— 859.

15. Zhang B., Chen J., Coddet C. Microstructure and transformation behavior of in-situ shape memory alloys by selective laser melting Ti—Ni mixed powder. J. Mater. Sci. Technol. 2013. Vol. 29. P. 863—867.

16. Vrancken B., Thijs L., Kruth J.-P., Humbeeck J. Van. Microstructure and mechanical properties of a novel β titanium metallic composite by selective laser melting. Acta Mater. 2014. Vol. 68. P. 150—158.

17. Murr L.E., Gaytan S.M., Ceylan A., Martinez E., Martinez J.L., Hernandez D.H., Machado B.I., Ramirez D.A., Medina F., Collins S., Wicker R.B. Characterization of titanium aluminide alloy components fabricated by additive manufacturing using electron beam melting. Acta Mater. 2010. Vol. 58. P. 1887—1894.

18. Schwerdtfeger J., Körner C. Selective electron beam melting of Ti—48Al—2Nb—2Cr: Microstructure and aluminium loss. Intermetallics. 2014. Vol. 49. P. 29—35.

19. Biamino S., Penna A., Ackelid U., Sabbadini S., Tassa O., Fino P., Pavese M., Gennaro P., Badini C. Electron beam melting of Ti—48Al—2Cr—2Nb alloy: Microstructure and mechanical properties investigation. Intermetallics. 2011. Vol. 19. P. 776—781.

20. Gussone J., Hagedorn Y.-C., Gherekhloo H., Kasperovich G., Merzouk T., Hausmann J. Microstructure of γ-titanium aluminide processed by selected laser melting at elevated temperatures. Intermetallics. 2015. Vol. 66 P. 33—140.

21. Li W., Liu J., Wen S., Wei Q., Yan C., Shi Y. Crystal orientation, crystallographic texture and phase evolution in the Ti—45Al—2Cr—5Nb alloy processed by selective laser melting. Mater. Character. 2016. Vol. 113. P. 125— 133.

22. Peng J., Mao Y., Li S., Sun X. Microstructure controlling by heat treatment and complex processing for Ti2AlNb based alloys. Mater. Sci. Eng. A. 2001. Vol. 299. P. 75—80.

23. Jia J., Zhang K., Jiang S. Microstructure and mechanical properties of Ti—22Al—25Nb alloy fabricated by vacuum hot pressing sintering. Mater. Sci. Eng. A. 2014. Vol. 616. P. 93—98.

24. Wu J., Xu L., Lu Z., Lu B., Cui Y., Yang R. Microstructure design and heat response of powder metallurgy Ti2AlNb alloys. J. Mater. Sci. Technol. 2015. Vol. 31. P. 1251—1257.